The inventor of the present invention and others have proposed a technology of a recording/reproducing apparatus using SNDM (Scanning Nonlinear Dielectric Microscopy) for nanoscale analysis of a dielectric recording medium. In the SNDM, by using a plurality of conductive probes having a small projective portion on the tip, which are used for atomic force microscopy (AFM) or the like, the resolution of measurement can be increased to sub-nanometer. Recently, by applying the technology of SNDM, a super high-density recording/reproducing apparatus has been developed, wherein the recording/reproducing apparatus records data into a recording medium having a recording layer made of a ferroelectric material (refer to a patent document 1).
On the recording/reproducing apparatus using such SNDM, the information is reproduced by detecting the positive/negative direction of polarization of the recording medium. This is performed by using the fact that the oscillation frequency of a LC oscillator, which includes a high-frequency feedback amplifier including a L component, the electrically conductive probe mounted on the amplifier, and the capacitance Cs of a ferroelectric material under the probe, is changed by a change ΔC in small capacitance, which is caused by the extent of a non-linear dielectric constant due to the distribution of the positive/negative polarization. That is, this is performed by detecting a change in the distribution of the positive/negative polarization, as a change in oscillation frequency Δf.
Moreover, in order to detect the difference in the positive/negative polarization, an alternating electric field is applied at sufficiently lower frequency than the oscillation frequency, by which the oscillation frequency changes with the alternating electric field. At the same time, a ratio of the change in the oscillation frequency, including a code or sign, is determined from the non-linear dielectric constant of the ferroelectric material under the probe. Moreover, by FM (Frequency Modulation)-demodulating and extracting a component caused by the alternating electric field, from a high-frequency signal of the LC oscillator, which is FM-modulated in accordance with the change ΔC in the small capacitance associated with the application of the alternating electric field, the record information recorded in the ferroelectric recording medium is reproduced.
The plurality of probes used here are arranged in a one-dimensional or two-dimensional matrix on a circuit substrate. Moreover, if signals detected on the respective plurality of probes are processed, independently and simultaneously, a plurality of signal processing devices, which correspond to the respective plurality of probes, are formed on the same circuit substrate. At this time, in order to form the signal processing devices (more specifically, the aforementioned LC oscillators or the like) correspondingly to the probes, the size of each of the signal processing devices needs to be determined depending on an interval in the arrangement of the probes
Patent document 1: Japanese Patent Application Laying Open NO. 2003-085969